THE CONQUEST OF TIME AND SPACE 



man was relieved of one of his perilous tasks, which on 

 freight trains took a heavy toll in loss of lives. 



This relatively simple, and usually effective, sys- 

 tem had two grave defects. The first of these lay in 

 the fact that if there was a leak — even a very small one 

 — anywhere along the line of the train pipe or the brake 

 cylinders, the brakes would not work, the compressed 

 air being exhausted into the atmosphere instead of act- 

 ing on the brake cylinders. The common accident of 

 having his train "break in two" rendered the engineer 

 powerless to stop the cars, and disastrous "runaways'' 

 sometimes resulted. The second defect, which became 

 more and more apparent as the length of trains was in- 

 creased, was the impossibihty of applying the air to 

 the brakes of the rear cars as quickly as to those near 

 the engine, since the compressed air could not travel 

 the length of the train pipe instantaneously, on account 

 of the frictional resistance. 



These defects were quickly recognized by Mr. West- 

 inghouse, and in 1876, seven years after he applied his 

 first invention, he produced his automatic air brake 

 which overcame them effectually. In this brake the 

 train pipe and the air reservoir were retained as in the 

 straight air brake system, but in addition each car was 

 equipped with a storage reservoir of sufficient size to 

 supply the brake cylinder. In place of the older ar- 

 rangement in which the train pipe simply retained air 

 at atmospheric pressure when not in use, the new sys- 

 tem kept the air in the train pipe under a considerable 

 pressure at all times when the brake was not in use. 

 And, reversing the conditions of the straight air brake, 



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